Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
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Endothelins (ETs) bind to two types of receptor: ETA and ETB. We examined the ET receptor types in the pig coronary artery smooth muscle, contractions they produced, their Ca2+- pool utilization and peroxide sensitivity. In Ca2+-containing solution, ET-1 (a non-selective agonist) and IRL1620 (selective ETB agonist) contracted the de-endothelialized rings but the contractions with IRL1620 were much smaller. In Ca2+-free solution, ET-1 contractions were decreased much greater than IRL1620. Treating the rings with peroxide inhibited the contractions produced by both the agents with the following IC50 values in mM: ET-1 in Ca2+ 1.2, ET-1 in Ca2+-free 1.4, IRL1620 in Ca2+ 0.24, and IRL1620 in Ca2+-free 0.14. Pretreating microsome with peroxide did not affect the binding to either receptor types. Cells cultured from this smooth muscle expressed only ETA receptors and ET-1 produced an increase in cytosolic Ca2+. Treating these cells with 0.3 mM peroxide inhibited < 95% of this increased. We conclude that: ETB contractions depend more in intracellular Ca2+- stores than ETA, ETB is more susceptible to peroxide, and ETA mediated Ca2+-mobilization is more susceptible to peroxide than contraction suggesting that ETA contraction has a Ca2+- independent mechanism(s) which is resistant to peroxide. Supported by HSFO.

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Poster Number PAelmoselhi0138
Keywords: Ca2+, Endotholin, Free radicals, Smooth muscle, ET receptor